.TH MPI_T_pvar_read 3 "6/7/2023" " " "MPI"
.SH NAME
MPI_T_pvar_read \-  Read the value of a performance variable 
.SH SYNOPSIS
.nf
.fi
.nf
int MPI_T_pvar_read(MPI_T_pvar_session session, MPI_T_pvar_handle handle,
void *buf)
.fi


.SH INPUT PARAMETERS
.PD 0
.TP
.B session 
- identifier of performance experiment session (handle)
.PD 1
.PD 0
.TP
.B handle 
- handle of a performance variable (handle)
.PD 1

.SH OUTPUT PARAMETERS
.PD 0
.TP
.B buf 
- initial address of storage location for variable value (choice)
.PD 1

.SH NOTES
The MPI_T_pvar_read() call queries the value of the performance variable with the
handle "handle" in the session identified by the parameter session and stores the result
in the buffer identified by the parameter buf. The user is responsible to ensure that the
buffer is of the appropriate size to hold the entire value of the performance variable
(based on the datatype and count returned by the corresponding previous calls to
MPI_T_pvar_get_info() and MPI_T_pvar_handle_alloc(), respectively).

The constant MPI_T_PVAR_ALL_HANDLES cannot be used as an argument for the function
MPI_T_pvar_read().

.SH THREAD AND INTERRUPT SAFETY

This routine is thread-safe.  This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks.  However, the routine is not interrupt safe.  Typically,
this is due to the use of memory allocation routines such as 
.I malloc
or other non-MPICH runtime routines that are themselves not interrupt-safe.

.SH ERRORS

All MPI routines (except 
.I MPI_Wtime
and 
.I MPI_Wtick
) return an error value;
C routines as the value of the function and Fortran routines in the last
argument.  Before the value is returned, the current MPI error handler is
called.  By default, this error handler aborts the MPI job.  The error handler
may be changed with 
.I MPI_Comm_set_errhandler
(for communicators),
.I MPI_File_set_errhandler
(for files), and 
.I MPI_Win_set_errhandler
(for
RMA windows).  The MPI-1 routine 
.I MPI_Errhandler_set
may be used but
its use is deprecated.  The predefined error handler
.I MPI_ERRORS_RETURN
may be used to cause error values to be returned.
Note that MPI does 
.B not
guarantee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.

.PD 0
.TP
.B MPI_SUCCESS 
- No error; MPI routine completed successfully.
.PD 1
.PD 0
.TP
.B MPI_T_ERR_INVALID 
- Invalid use of the interface or bad parameter values(s).
.PD 1
.PD 0
.TP
.B MPI_T_ERR_INVALID_HANDLE 
- The handle is invalid.
.PD 1
.PD 0
.TP
.B MPI_T_ERR_INVALID_SESSION 
- Session argument is not valid.
.PD 1
.PD 0
.TP
.B MPI_T_ERR_NOT_INITIALIZED 
- The MPI tool information interface is not initialized.
.PD 1
.PD 0
.TP
.B MPI_ERR_OTHER 
- Other error; use 
.I MPI_Error_string
to get more information
about this error code. 
.PD 1

